BANGKOK — Thailand’s military junta said Monday that it would stay in power “indefinitely” and that its rule had been endorsed by King Bhumibol Adulyadej, the monarch for nearly seven decades who has semi-divine status in the country.

Gen. Prayuth Chan-ocha, who overthrew the elected government on Thursday, said during a news conference that the military would create a “genuine democracy” but gave no time frame for doing so. “It will depend on the situation,” he said, before hastily leaving a podium as he was questioned by reporters.

Amid small but daily protests against the coup, General Prayuth warned that the junta would become “more strict” if resistance continued.

An endorsement by the king, who is 86 years old and ailing, is crucial for the coup leaders. After Thailand’s previous coup, in 2006, the top general was photographed prostrating himself before the king.

King Bhumibol is above criticism both by tradition and law; insulting him, the queen or the crown prince is punishable by up to 15 years’ imprisonment under a law that has been broadly interpreted by the authorities in recent years. The military said over the weekend that all lèse-majesté cases would now be heard in military courts.

<== Gen. Prayuth Chan-ocha said at a news conference Monday that the military would create a “genuine democracy” but gave no time frame for doing so.Credit Damir Sagolj/Reuters

The king has not been seen in public since Thursday’s coup, and no member of the royal family has spoken publicly about the military takeover. The Royal Gazette, which lists official government decisions, carried the announcement of General Prayuth’s royal appointment.

“In order to maintain the peace and order of the nation and the reconciliation of the people, there shall be a royal command to officially endorse the appointment of General Prayuth Chan-ocha as the leader of the National Council for Peace and Order to administrate the country from here onward,” the announcement said.

The National Council for Peace and Order is the name the junta has chosen for itself.

General Prayuth, who wore a formal white uniform for his appearance on Monday, was flanked by top officers of the armed forces who stood in front of emblems of the military and the official seal of Thailand’s monarchy.

General Prayuth spoke in vague terms about “measures to make sure there are no further problems.”

But he also offered signs that the military was overwhelmed with the administration of the country. He urged all sides “not to make any more requests.”

The government installed by the military after the last coup in 2006 was widely criticized as a failure, and some commentators have expressed concern that the military will not be able to handle the management of a country of 67 million.

“People may wonder if we are competent or not,” General Prayuth said Monday. “I would say with determination I can do everything.”

General Prayuth, 60, was expected to retire as the head of the army later this year. But the coup is likely to prolong his career in the military, one of Thailand’s most powerful institutions and one that has a history of coups and suppression of popular movements. General Prayuth was the deputy head of the army when troops used assault weapons to violently crack down on protesters in the heart of Bangkok in 2010, leaving dozens of people dead and hundreds injured, including many bystanders.

A career soldier who is reported to be close to the palace, General Prayuth appeared reluctant to intervene in the political crisis. But he often masks his intentions with sarcastic and combative wit in public appearances.

After his speech Monday, General Prayuth tried to avoid questions. “If you want me to talk a lot, I won’t have time to work,” he said. “Don’t ask me a lot of questions.”

The junta on Monday released from detention the leaders of the protest movement who had sought to overthrow the former government through street protests. The coup has been seen as a victory for the protest leaders, who had blocked elections that they were almost certain to lose and repeatedly pleaded for the military’s intervention.

Among those released was Suthep Thaugsuban, the main protest leader, who was taken by soldiers to the attorney general’s office to hear formal charges of rebellion. It was unclear whether the attorney general would follow through with the charges, which were lodged when the government removed last week was still in power.

Mr. Suthep, who was also charged with murder for ordering the crackdown on protesters when he was deputy prime minister in 2010, was released on bail.

The Thai news media also reported that Yingluck Shinawatra, the former prime minister, was released from military detention but that she had not appeared in public by Monday evening.

The junta has summoned around 250 people since overthrowing the government on Thursday, but at least two members of the former governing party have refused to give themselves up.

In one of the junta’s first policy decisions, General Prayuth said Monday that it would order that farmers be paid money owed to them from a costly subsidy program. The money was held up because the government was barred from borrowing or passing a budget while the country awaited elections. Protesters, led by Mr. Suthep, had blocked elections as a way of creating a power vacuum.

The military had refused to take sides during the six months of protests. Mr. Suthep, a career politician and back-room political dealmaker from southern Thailand, had the backing of some of the wealthiest families in Bangkok. Ms. Yingluck’s party has its power base in the provinces and was founded by a polarizing former prime minister, Thaksin Shinawatra, a tycoon who was accused of mixing his personal businesses with matters of state. Mr. Thaksin lives overseas but retains influence over his party.

A version of this article appears in print on May 27, 2014, on page A9 of the New York edition with the headline: After Coup, General Vows to Create A ‘Genuine Democracy’ in Thailand.